BirdAnalyst
Species · Washington · BBS 2025 Release · 1966–2024

Black Tern Population Trend in Washington

All statesWetland birds

Black Tern in Washington has fallen sharply: down 53% on the route-weighted index since 1970.

-53%Since 1970TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
12Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
43YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black Tern Trends in WashingtonNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

long arc declinecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Black Tern has fallen sharply in Washington: down 53% on the route-weighted index since 1970.

Black Tern Population Forecast in Washington

If the recent trend holds, Black Tern in Washington is projected to rise about 172% by 2026 — from 0.06 in 2021 to a central estimate of 0.16 (95% range 0.00–0.39). A 5-year backtest shows a typical error of ±488%, with 100% of held-out values landing inside the 95% band.

+172%Change by 2026TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
0.16Projected 2026 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.3995% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±488%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Black Tern in Washington is projected to rise about 172% by 2026 — from 0.06 in 2021 to a central estimate of 0.16 (95% range 0.00–0.39). A 5-year backtest shows a typical error of ±488%, with 100% of held-out values landing inside the 95% band.19682026
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20220.160.000.39
20230.160.000.39
20240.160.000.39
20250.160.000.39
20260.160.000.39

Black Tern Survey Routes in Washington

Routes recording Black Tern in Washington.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Turnbull Nwr420211993
Malden420121998
Brewster320001980
Ewan220191985
Ellensburg219981998
Moses Lake219901990
Curlew219921992
Twin Lakes220102010
Chewelah120122012
Harrington119801980
Reardan119901968
Potholes120061996

Black Tern Population Trend in Other States

californiacoloradoidahoillinoisindianaiowakansasmainemichiganminnesotamissourimontananebraskanevadanew-yorknorth-dakotaohiooregonsouth-dakotatexasutahwisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.